Mechanistic investigations of the oxidation of phenethyl alcohols by sodium-N-bromo- benzenesulphonamide in acid medium

摘要

The kinetics of oxidation of six substituted phenethyl alcohols (X-C_6H_4-CH_2-CH_2-OH where X = -H, -C1, -Br, -CH_3, -OCH_3 and -NO_2) by sodium-N-bromo-benzenesulphonamide or bromamine- B(BAB) in the presence of HC1 at 35°C showed that the rate hasfirst-order dependence on [BAB]_0 and [H ~+] and fractional order on [PEA]_0 and [Cl~-]. Ionic strength variations, addition of reaction product of benzenesulphonamide and variation of dielectric constant of the medium have no effect on the rate. The solvent isotope effect k~1(H_2O)/ k~1 (D_2O) = 0.82. Proton inventory studies have been made in H_2O-D_2O mixtures. The Hammett plot is biphasic and the reaction constant p was — 3.2 for electron-releasing substituents and — 0.34 for electron-withdrawinggroups. The activation parameters triangle openH~#, triangle openS~# follow an isokinetic relationship.